Light

● Option (a) : A wooden board does not reflect the light it blocks the light because it is opaque hence we cannot see the patch of light by placing wooden board in position A. Therefore the option (a) is incorrect.

● Option (b) : A glass sheet does not reflect the light it allows light to pass through it because it is transparent hence we cannot see the patch of light by placing glass sheet in position A. Therefore the option (b) is incorrect.

● Option (c) : A mirror reflect the light and the direction of light changes when it falls on the mirror hence we can see the patch of light by placing mirror in position A. Therefore the option (c) is correct.

● Option (d) : A sheet of white paper does not reflect the light hence we cannot see the patch of light by placing wooden board in position A. Therefore the option (d) is incorrect.

The image formed by pin hole camera is inverted and left - right reversed.

● Option (a) : the image is not inverted. Hence option (a) is incorrect.

● Option (b) : the image is inverted and left – right reversed. Therefore the option (b) is correct.

● Option (c) : the image is not inverted. Therefore the option (c) is not correct.

● Option (d) : the image is inverted but not left – right reversed. Therefore the option (d) is incorrect.

The light always travels in the straight line. Hence if tubes are straight than the student will be able to see the light.

● Option (a) : the tube in option (a) is not straight. Therefore we will not be able to see the candle flame clearly.

● Option (b) : the tube in the given option is curved. Therefore we will not be able to see the candle flame clearly. Hence the option (b) is incorrect.

● Option (c) : the tube in option (c) is bent. Therefore we will not be able to see the candle flame clearly.

● Option (d) : the tube in option (a) is straight. Therefore we will be able to see the candle flame clearly. Hence the correct answer is (d)

Any source of light, opaque object and screen are necessary to form a shadow.

● Option (a) : the sun is not necessary to form a shadow because we can form shadow from some other sources of light also like torch etc. Hence the answer is option (a).

● Option (b) : screen is necessary to take the image.

● Option (c) : any source of light is necessary to form the shadow like torch, bulb, streetlight etc.

● Option (d) : the opaque object is necessary to block the light.

with the change in the time the direction of sun also changes hence the direction of source of light changes. Therefore the shape and size of the shadow changes.

● Option (a) : above option is not correct because it says that shape of the shadow will change but size will not change.

● Option (b) : above option is not correct because it says that size of the tree will change but shape of the shadow will not change.

● Option (c) : since both size and shape of the shadow changes. Therefore the option (c) is the correct answer.

● Option (d) : above option is not correct because it says that neither size nor shape of the shadow will change.

For forming the circular shadow the object should have a circular shape.

● Option (a) : A ball is circular in shape hence it can form a circular shadow.

● Option (b) : A flat disc is circular in shape hence it can also form a circular shadow.

● Option (c) : A shoe box is not circular in shape hence it cannot form a circular shadow. Therefore it is the correct answer.

● Option (d) : an ice cream cone is circular in shape hence it can also form a circular shadow.

For the image formation the surface should be reflecting like mirror. Non reflecting or rough surfaces do not form the images.

● Option (a) : unpolished wood is non reflecting surface also it is rough and opaque. Hence it will not form the image. Hence it is not correct option.

● Option (b) : red stone is rough, opaque and non reflecting surface. Therefore it will not form the image of students. Hence it is incorrect.

● Option (c) : glass sheet is smooth and reflecting hence it will form the image of the students and students will be able to see it. Therefore the option (c) is correct answer.

● Option (d) : wood top covered with cloth is rough and it is also opaque hence it do not allow light to pass through it hence it will not form the image.

The same small circular image of the sun will be obtained in all the three cases because the small holes in the strips will act as a pinhole camera irrespective of their shapes. Also, as the light moves in the straight line, therefore the image of the sun will be same in all the cases. Diagram below shows the image that will be obtained.

“P” is the sheet of some transparent material like thin plastic, ground glass etc. Because only the transparent materials allows light to pass through them without changing the path of light. Since the path of light is not changed therefore we get image on screen. Therefore the “P” is some transparent materials. Figure below shows some of the transparent materials.

The light from the torch “C” will not form a shadow on the screen because the light always travels in the straight line due to which the light from “C” will go downward. Also the shadow is formed on the path from which the light is coming but there is no screen (Or opaque object) on downside to take the shadow, hence we will not get shadow from the torch “C”.

No there will not be any difference in the shadow because the size and shape of the shadow depends on the size and shape of the opaque object (metal bowl). Since the same metal bowl is used in the case A and B therefore the shadow will be same in both the cases.

(i)Correct Statement : The color of the shadow of an object does not depend on its color of the object.

Shadow is always black in color because shadow is formed when an opaque object absorbs all the light falling from the light source due to which no light is reflected and it looks black.

(ii) Correct Statement : Transparent objects allows most of the light to pass through them OR Translucent objects allows light to pass through them partially.

Transparent objects are the objects which allow most of the light to pass through them without disturbing the path of the light.

The Shadow of an object is formed when light from various light sources (torch, bulb, sun etc) falls on the object. If the light from more than one sources falls on the object than we can obtain more than one shadow of an object. For Example : during a football match we see many shadows of the single player because of the light falling on the players from various light sources present in the ground.

The figure below shows multiple shadows.

The bird or an airplane flying high in the sky do not cast their shadow on the ground because they are at very high altitude due to which the ground which acts as screen for the shadow is far away and in absence of the screen the shadow cannot be formed.

When they are at some lower height or near to the ground than we can see their shadow because ground acts as screen there and we see their shadow the ground. The figure below shows the shadow of bird flying near to the ground.

There are numerous ways to convert a transparent glass sheet into translucent some of them are as follows

1. By applying an oil, ghee, butter on it (this will allow the light to partially pass through the glass sheet).

2. Rubbing the surface of the glass by some materials like (sandpaper). This will make the glass sheet rough and light will pass through it partially.

The Position “A” will form the shadow ‘a’ as shown below.

The position “B” will form the shadow ‘b’ as shown in the figure below.

The size of the shadow is bigger in ‘a’ because the screen, torch, and the ball are in the same straight line in “A”. Whereas in “B” the torch is not in line with ball and screen.

No the color of the light will not affect the shadow because .Shadow is the dark patch formed when an object obstructs the path of the light. Hence no light reaches in the shadow region; due to which the color of the shadow is black. Hence the color of light will not affect the shadow color because light is obstructed by an opaque object.

Air around us is transparent due to which we can see the objects like trees, buildings, etc. But when the thick smoke, clouds, dust is present in the air than it does not remain transparent because dust, smoke etc absorbs the light. For Example during sandstorm we can’t see things due to dust present in the air.

The figure below shows the air mixed with smoke which makes it translucent we are not able to see buildings clearly.

Shadow is the dark patch formed when an object obstructs the path of the light. Hence no light reaches in the shadow region; due to which the color of the shadow is black. So the color of shadow is independent of the color of the object because light is always absent there. Therefore the color of shadows of all towels will be black.

Pinhole camera always forms the inverted image having same color as that of an object. Therefore the colors of the shirts will be same in the image but image will be inverted and left – right reversed as shown in the figure below.

Shadow is the dark patch formed when an object obstructs the path of the light. Therefore the color of the shadow will be black because light is always absent there, the shape of shadow will be same as the shape of the flower. The figure below shows the shadow of the flower formed on the screen.

We can see the shadow of the football lying on the ground because the ground acts as the screen, Source of light is the floodlights of the ground, and opaque object is football. Hence there are all necessary things for shadow formation so we can see the shadow of football on the ground as shown in the figure below.

When the football is kicked in the air the ground which is acting as the screen is very far away hence no shadow is formed because there is no screen on which we can see the shadow.

Some reasons due to which the shadow cannot be obtained are as follows.

1. When the screen is placed far away from the ball than he cannot get shadow on the screen.

2. The beam of light from the torch is falling parallel to the screen on the ball due to which the ball is not able to obstruct the whole light from the torch and shadow is not obtained.

3. The torch is kept away from the ball. This makes the source of light far away hence the sufficient light is not reached to the ball.

An accurate shadow of the ball will be formed only when the ball, torch, and screen are in the same straight line. The figure below shows the arrangement.

The shadow will not be formed in each case.

1. The muslin cloth will form the shadow but it will be lighter because muslin cloth is translucent due to which light will partially pass through it.

2. The transparent glass will not form the shadow because for formation of the shadow the object should be opaque because opaque objects do not allow light to pass through them, they obstructs the path of the light.

3. The sheet of plywood will form the perfect dark shadow because it is opaque hence it will obstruct all the light falling on it.